1. Field of the Invention
The invention relates to a method and devices for cylinder adjustment in which the contact pressure between cylinders is adjustable for the purpose of proper ink transfer between the respective cylinders.
2. Description of the Related Art
It has been heretofore known in the preparation and in the setting of printing machines to visually determine the force and the uniformity of the contact pressure across the entire width of the cylinder of an inking unit. A certain base amount of ink is introduced into the inking unit for that purpose, and distributed therein by way of rotation. When the cylinders are at a stillstand, a device is actuated which brings the ink-carrying cylinder into contact with an ink-receiving cylinder and then disengages the same. A contact strip is created on the ink-receiving cylinder whose width and whose shape provide an indication as to whether or not the pressure is sufficiently high and uniform. Depending on the result of the visual inspection of the contact strips, the contact pressure between the cylinders is increased or decreased with adjusting screws provided for the cylinder pressure adjustment. As seen along the width of the cylinders, the cylinder axes can be shifted in parallel relative to one another with the adjusting screws or they can be unevenly spaced from each another on their respective sides, such that the uniformity of the contact strip can be adjusted.
It has also been known to temporarily insert at least one paper strip between the cylinders. When the cylinders approach one another, a partial image is created on the paper strip from a partial area of the contact strip. The contact strip is then inspected visually. The inspection is not on the ink-receiving cylinder but by means of the reproduction. This method is advantageous when the visual accessibility in the inking unit does not allow for visual inspection or only to a limited degree.
It is disadvantageous in these prior methods that the visual inspection is error-prone and that the correct adjustment of the contact pressure between the cylinders depends on the experience of the operator.
Swiss patent CH 451 211 describes a device in which an especially formed testing body is provided for inspecting the adjustment of ink applicator rollers in a flat-bed high pressure machine. The testing body has defined dimensions and it serves as a gap gauge between the flat-bet form and the applicator roller. From the width of an ink strip, which the applicator rollers leave thereon, one can deduce the low position of the respective applicator roller. Besides the visual inspection and the expense in producing the testing body, this leads to the disadvantage that the inspection cannot be performed across the entire width of the applicator roller and that the testing body can hardly be utilized in rotary printing machines with barely accessible form rollers.
This is similarly the case with mechanically scanning devices, as for instance the one described in German patent 130 260. Feelers to be inserted underneath the roller are used there for adjusting the applicator rollers. The feelers cooperate through mechanical elements with an indicator for the position of the feeler. This leads to the additional disadvantage that, in order to prevent measurement errors, the feelers must be continually re-adapted to the variably resilient surface material on the rollers.
It has also been known heretofore in determining the contact pressure between two cylinders to dispose pressure sensors on the peripheral surface of one of the cylinders. The sensors provide signals which are proportional to the contact pressure and the signals can be used to adjust the contact pressure (DE 36 14 436 A1). Such a solution is logically very expensive because a multitude of pressure sensors must be provided over the entire peripheral surface and the signals must be transmitted from the rotating cylinders with special devices.